FINE ARTS.
DAGUERRICS APPARATUS OF PHOTOGRAPHY.
THE process of Photographic Drawing wits publicly-exhibited by DACUERRE, by order of the Minister of the Interior, on the Quai D'Orsai, Paris, on the 7th instant. The following account of the ope- ration as performed on that occasion, from the Journal des Daats, snore satisfactorily describes the apparatus and process than any previous one that we have seen.
M. DAGITELIRE took a plate of copper plated with silver, (not silvered merely,) and rubbed the silver surface slightly with sweet-oil, and very, fine pumice-powder, malting use of little balls of cotton wool. The object of this operation is to cleanse and dull the surface completely ; and in performing it, it is necessary to rub first with a circular motion,. and afterwards in straight lines. That done, he washed the plate with a solution of nitric acid, composed of sixteen parts. distilled water and one of acid : the plate was then slightly warmed by passing it over the flame of a lamp, with the silver surface uppermost ; and the washing with diluted nitric acid, as before, was repeated. It was now ready to receive the coating of iodine ; which was thus applied. The light, being excluded by closing the shutters of the apartment, the plate, fixed on a small board, was placed, with the silver surface downwards, over an aperture the size of the picture required, in the lid of a box, at the bottom of which was the iodine ; half-way in the depth of the box was a wooden frame on which a piece of muslin was strained ; as the iodine evaporated, the fumes rose through the muslin, and were thus diffused equally over the surface of the plate, forming on the silver a coating of iodide of silver, the colour of brass.
The plate thus prepared was placed in the camera obscura—the focus having been previously adjusted by trying the effect of the picture on a piece of ground glass ; and it was suffered to remain till the action of the sun's rays on its surface was considered sufficient. The time re.: quired varies from seven marinates to forty, according to the season and the state of the weather; and as not the slightest trace of the effects of light is visible on the plate, the judgment of the operator derived from experience is his only guide. In withdrawing the plate, great care must be taken that no light whatever falls on it, previous to the opera- tion that follows. The plate was then fixed, at an auglc of 45 degrees,
in a box, at the bottom of which was placed about two pounds of mer- cury in an earthern pan : the mercury was heated to 65 centigrade, (about 117 degrees Fahrenheit,) by means of a lamp beneath the pan ; and the globules of mercury rising combined with the surface of the plate, till in a few minutes the picture appeared. This operation was watched through a piece of glass inserted in front of the box ; and the moment 'it was completed, the plate was taken out and washed with dis- tilled water saturated with common salt, or with hyposulphite of soda, heated to a degree below the boiling-point : the process was then com- pleted. g. DAGLIERTIE observed, for the information of those who wished to make trial of the process, that after the iodide of silver has formed, the plate, if kept from the action of light, can remain for an hour without risk of danger ; and that after the view is transmitted as above, it can remain excluded from light for four hours without injury, before sub- mitting it to the operation of the vapour of mercury.
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